Cross-flow fan and air conditioner equipped with same

ABSTRACT

A crossflow fan includes an impeller formed by plate-like blades  42.  Each blade  42  is inclined such that the outer edge  42   a  is located on the leading side of the inner edge  42   d  with respect to the rotation direction of the impeller  41.  The face of each blade  42  that is located on the leading side of the rotation direction forms a positive pressure surface  42   p,  and a face located on the trailing side forms a negative pressure surface  42   q.  Notches  42   b  are formed at the outer edge  42   a  of the blade  42 . The notches  42   b  are arranged at predetermined intervals along the rotation axis of the impeller. The bottom  42   y  of the notch  42   b  is connected to the positive pressure surface  42   p  at a positive pressure corner  42   n  and connected to the negative pressure surface  42   q  at a negative pressure corner  42   m.  The positive pressure corner  42   n  and the negative pressure corner  42   m  are both rounded.

TECHNICAL FIELD

The present invention relates to a crossflow fan and an air conditioner having the crossflow fan.

BACKGROUND ART

Crossflow fans are known as air blowers as used in an indoor unit of a wall-mounted air conditioner. FIG. 14 shows one example of a crossflow fan. As shown in FIG. 14, a crossflow fan 104 is a type of fan through which air flow crosses transversely, and includes an impeller 141 formed by a number of blades 142. The blades 142 are forward-swept blades, in each of which the outer edge is located on the leading side from the inner edge with respect to the rotation direction Z1. When the impeller 141 is rotated in the rotation direction Z1 by an electric motor, cooled or heated air flow X (that is, conditioned air flow) in an indoor unit 1 of the air conditioner transversely passes through the impeller 141, in a plane perpendicular to the rotation axis Z of the impeller 141.

In the impeller of such a crossflow fan, air passing through the blades of the impeller generates noise. In an attempt to reduce such noise with a simple structure, crossflow fans have been proposed that have a plurality of notches formed at an edge of each blade (for example, see Patent Document 1). FIGS. 15( a) and 15(b) are perspective views showing an impeller blade of such a crossflow fan. As shown in FIGS. 15( a) and 15(b), a plurality of notches 242 b are formed at predetermined intervals at an outer edge 242 a of a plate-like blade 242. A straight section 242 c is formed between each adjacent pair of the notches 242 b. As shown in FIG. 16, the bottom 242 y of each notch 242 b extends in a direction substantially perpendicular to the sides of the blade 242. The notches 242 b, which are formed in the blade 242 as described above, reduce trailing vortices (not shown) generated at an outlet region M of a crossflow fan 204. In other words, a simple modification to the shape of the blade 242 effectively reduces the noise of the crossflow fan 204.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-125390 DISCLOSURE OF THE INVENTION

Problems that the Invention is to Solve

As described in Patent Document 1, a simple structure where notches are formed at an edge of each blade can effectively reduce noise. However, when employed, this structure increases air resistance against rotation of the impeller 241. Specifically, when notches 242 b are formed at the outer edge 242 a of each blade 242 as shown in FIG. 16, rotation of the impeller 241 causes air flow X to strike the bottom 242 y of each notch 242 b, which extends perpendicularly to both sides of the blade 242. Thus, compared to a case where no notches are formed at the outer edge 242 a, collision of the air flow X generates greater air resistance against rotation of the impeller 241 at an inlet region N of the crossflow fan 204. As a result, to ensure a sufficient volume of discharged air from the crossflow fan 204, the power output of the electric motor, which drives the crossflow fan 204, needs to be increased.

Accordingly, it is an objective of the present invention to provide a crossflow fan that prevents the power output required from an electric motor driving the crossflow fan from being increased, and an air conditioner having the crossflow fan.

Means for Solving the Problems

To achieve the foregoing objective and in accordance with one aspect of the present invention, a crossflow fan is provided that includes an impeller having a plurality of support plates located on a rotation axis of the impeller and a plurality of plate-like blades provided at peripheral portions of the support plates. The blades extend parallel to the rotation axis. Each blade is inclined such that its outer edge is located on the leading side of its inner edge with respect to the rotation direction of the impeller. One of the faces of each blade that is on the leading side of the rotation direction of the impeller forms a positive pressure surface. The face on the trailing side of the rotation direction forms a negative pressure surface. A plurality of notches are formed at the outer edge of each blade. The notches are arranged at predetermined intervals along the rotation axis of the impeller. At least one of a positive pressure corner and a negative pressure corner, which connect the bottom of each notch with the positive pressure surface and the negative pressure surface, respectively, is rounded.

Since the notches are formed in the outer edge of the blade, noise is effectively reduced with a simple structure. At least one of the positive pressure corner and negative pressure corner, which connect the bottom of the notch with the positive pressure surface and the negative pressure surface, respectively, is rounded. Therefore, air that flows into the notches from the outer side of the blade is allowed to flow smoothly into the impeller along the negative pressure surface and the positive pressure surface. This reduces the collision loss generated when air flows in from outside of the blade. As a result, required increased power output from the electric motor driving the crossflow fan caused by the formation of the notches in the blades can be reduced. In the above, the predetermined intervals may be the same intervals or may vary according to the position in the longitudinal direction of the blade.

In accordance with the present invention, the negative pressure corner, which connects the bottom of each notch with the negative pressure surface, may be rounded.

Also, in accordance with the present invention, the positive pressure corner, which connects the bottom of each notch with the positive pressure surface, may be rounded.

To achieve the foregoing objective and in accordance with one aspect of the present invention, a crossflow fan is provided that includes an impeller having a plurality of support plates located on a rotation axis of the impeller and a plurality of plate-like blades provided at peripheral portions of the support plates. The blades extend parallel to the rotation axis. Each blade is inclined such that its outer edge is located on the leading side of its inner edge with respect to the rotation direction of the impeller. One of the faces of each blade that is on the leading side of the rotation direction of the impeller forms a positive pressure surface. The face on the trailing side of the rotation direction forms a negative pressure surface. A plurality of notches are formed at the outer edge of each blade. The notches are arranged at predetermined intervals along the rotation axis of the impeller. The bottom of each notch is formed as a smooth curved surface that protrudes as a whole outward of the impeller.

Since the notches are formed in the outer edge of the blade, noise is effectively reduced with a simple structure. Further, since the bottom of each notch is formed to be a smooth curved surface that protrudes as a whole toward the outer circumference of the impeller, air that flows into the notches from the outer side of the blade is allowed to flow smoothly into the impeller along the negative pressure surface and the positive pressure surface. This reduces the collision loss generated when air flows into the notches from outside of the blade. As a result, required increased power output from the electric motor driving the crossflow fan can be reduced. In the above, the predetermined intervals may be the same intervals or may vary according to the position in the longitudinal direction of the blade.

In the present invention, the notches are preferably V-shaped as viewed from the negative pressure surface and the pressure surface of the blade,

According to this configuration, a greater pressure receiving area of the blade is ensured compared to a case where the notch has a rectangular shape.

Further, the present invention also provides an air conditioner having a crossflow fan having the above described configuration.

EFFECTS OF THE INVENTION

According to the present invention, since the notches are formed in the outer edge of the blade, noise is effectively reduced with a simple structure. At least one of the positive pressure corner and negative pressure corner, which connects the bottom of the notch with the positive pressure surface and the negative pressure surface, respectively, is rounded. Therefore, air that flows into the notches from the outer side of the blade is allowed to flow smoothly into the impeller along the negative pressure surface and the positive pressure surface. This reduces the collision loss generated when air flows in from outside of the blade. As a result, required increased power output from the electric motor driving the crossflow fan caused by the formation of the notches in the blades can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic diagram showing an indoor unit of an air conditioner having a crossflow fan according to one embodiment of the present invention;

FIG. 2 is a perspective view showing the crossflow fan according to the first embodiment;

FIGS. 3( a) and 3(b) are perspective views showing an impeller blade of the crossflow fan;

FIG. 4 is a diagram for explanatory illustration of a blade with notches;

FIG. 5 is a cross-sectional view of the blade taken along line 5-5 of FIG. 4;

FIG. 6 is a perspective view showing a cross section of a notch;

FIG. 7 is a diagram for explanatory illustration of a manner in which air flows into notches;

FIG. 8 is a cross-sectional view showing a blade according to a modified embodiment;

FIG. 9 is a cross-sectional view showing a blade according to another modified embodiment;

FIG. 10 is a cross-sectional view showing a blade according to a further modified embodiment;

FIGS. 11( a) and 11(b) are perspective views showing a blade according to yet another modification;

FIG. 12 is a diagram for explanatory illustration of the blade of the modified embodiment of FIG. 11;

FIG. 13 is a perspective view showing a cross section of a notch of the modification of FIG. 11;

FIG. 14 is a diagram for explanatory illustration of the prior art crossflow fan:

FIGS. 15( a) and 15(b) are perspective views showing an impeller blade of the prior art crossflow fan;

FIG. 16 is a diagram for explanatory illustration of the prior art crossflow fan.

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the present invention will now be described with reference to FIGS. 1 to 7.

As shown in FIG. 1, an air conditioner according to the present embodiment includes a wall-mounted indoor unit 1. The indoor unit 1 includes a main casing 2, a heat exchanger 3 arranged in the main casing 2, and a crossflow fan 4. The crossflow fan 4 has an impeller 41 having plate-like blades 42. The impeller 41 is driven by an electric motor (not shown) to compress and send air from an inlet region N to an outlet region M.

Air inlet ports 21 are provided in upper and front face of the main casing 2. An air outlet port 22 is provided in a lower face of the main casing 2. At the air outlet port 22, vertical flaps 23 and a horizontal flap 24 for adjusting the direction of air discharged from the air outlet port 22 are provided.

A guide portion 25 is formed in the main casing 2 at a position in the vicinity of the outlet region M of the crossflow fan 4. The guide portion 25 defines the passage of air discharged by the crossflow fan 4. A backflow preventing tongue 26 is formed at the air outlet port 22. The backflow preventing tongue 26 separates the outlet region M and the inlet region N from each other, thereby preventing discharged air from flowing back.

The heat exchanger 3 is located between the air inlet port 21 and the impeller 41, and formed by a front heat exchanging section 3 a and a back heat exchanging section 3 b. The front heat exchanging section 3 a is located in the main casing 2 near the front face. The back heat exchanging section 3 b is continuously formed at the top of the front heat exchanging section 3 a, and is located in the main casing 2 near the back face.

According to the above shown structure, when the impeller 41 of the crossflow fan 4 is driven by the electric motor, air in the room is drawn in to the main casing 2 through the inlet port 21. The air is cooled or heated by passing through the heat exchanger 3, and is discharged into the room through the air outlet port 22. Accordingly, conditioned air is delivered to the room.

As shown in FIG. 2, the impeller 41 of the crossflow fan 4 is formed by a great number of the blades 42, circular support plates 43, and an input shaft 44. The support plates 43 support the blades 42 and are located on the rotation axis A1 of the impeller 41. The input shaft 44 is connected to the electric motor and extends along the rotation axis A1. The support plates 43 are arranged parallel to each other at predetermined intervals along the rotation axis A1 of the impeller 41, or the longitudinal direction of the blades 42. The blades 42 are fixed to peripheral portions 43 a of the support plates 43 and arranged between adjacent two support plates 43 to extend parallel to the rotation axis A1.

The structure of each blade 42 will be described with reference to FIGS. 3 and 4. As shown in FIG. 2, the blades 42 are forward-swept. That is, each blade 42 is inclined such that the outer edge 42 a is located on the leading side of the inner edge 42 d with respect to a rotation direction Z1 of the impeller 41. As shown in FIGS. 2 and 3, the face of each blade 42 that is located on the leading side of the rotation direction Z1 forms a positive pressure surface 42 p, and a face located on the trailing side forms a negative pressure surface 42 q. The blade 42 is also curved such that the outer edge 42 a is located on the leading side of the inner edge 42 d with respect to the rotation direction Z1 of the impeller 41.

Notches 42 b are formed at the outer edge 42 a of the blade 42. The notches 42 b are arranged at predetermined intervals along the rotation axis A1 of the impeller 41. The notches 42 b are V-shaped when viewed from the negative pressure surface 42 q and the positive pressure surface 42 p of the blade 42. A basic shape section 42 c is formed between each adjacent pair of the notches 42 b. The basic shape sections 42 c form the curved basic shape of the blade 42. The width of the space between adjacent notches 42 b may be constant or may vary. For example, as shown in FIGS. 3 and 4, each end 6 a of the blade 42 with respect to the rotation axis A1 is close to the corresponding support plate 43. Thus, the flow velocity of air flow X at each end 6 a is greater than that in a center 6 b of the blade 42 in the rotation axis A1. In the present embodiment, the space between notches 42 b at each end 6 a of the blade 42 is greater than the space between notches 42 b at the center 6 b of the blade 42. This ensures a sufficient pressure receiving area at each end 6 a of the blade 42.

The notches 42 b may have the same size, but may have different sizes depending on position on the rotation axis A1. In the present embodiment, notches 42 b at each end 6 a of the blade 42 in the rotation axis A1 have a smaller size than notches 42 b at the center 6 b of the blade 42. This ensures a sufficient pressure receiving area at each end 6 a of the blade 42.

As described above, the notches 42 b formed at the outer edge 42 a of the blade 42 at predetermined intervals, and the basic shape sections 42 c are each formed between adjacent notches 42 b as shown in FIG. 4. This reduces trailing vortices (not shown) generated at the outlet region M of the crossflow fan 4, so that noise is reduced with a simple structure.

The notches 42 b are V-shaped when viewed from the negative pressure surface 42 q and the positive pressure surface 42 p of the blade 42. Thus, compared to a case where notches 42 b have rectangular shapes, the pressure receiving area of the blade 42 is enlarged.

FIG. 5 is a cross-sectional view of the blade 42 taken along line 5-5 of FIG. 4, and FIG. 6 is a perspective view showing a cross section of a notch 42 b. As shown in FIGS. 5 and 6, the bottom 42 y of the notch 42 b is connected to the negative pressure surface 42 q at a negative pressure corner 42 m, and connected to the positive pressure surface 42 p at a positive pressure corner 42 n. The negative pressure corner 42 m and the positive pressure corner 42 n are both rounded.

More specifically, the bottom 42 y of each notch 42 b, which extends perpendicularly to the negative pressure surface 42 q of the blade 42, and the negative pressure surface 42 q are smoothly connected to each other by the negative pressure corner 42 m. The bottom 42 y of each notch 42 b, which extends perpendicularly to the positive pressure surface 42 p of the blade 42, and the positive pressure surface 42 p are smoothly connected to each other by the positive pressure corner 42 n. Therefore, the length of the bottom 42 y, which extends perpendicularly to the positive pressure surface 42 p and the negative pressure surface 42 q, is less than that of the bottom 242 y of the prior art notch 242 b (see FIG. 16).

As described above, the negative pressure corner 42 m and the positive pressure corner 42 n are rounded to form smooth and curved surfaces. This allows the air flow X that flows into the notches 42 b from outside of the blade 42 to flow smoothly along the negative pressure surface 42 q and into the impeller 41. As a result, the collision loss generated when the air flow X flows from outside of the blade 42 into the notches 42 b is reduced.

The crossflow fan 4 according to the present embodiment has the following advantages.

(1) The positive pressure corner 42 n and the negative pressure corner 42 m, which connect the bottom 42 y of the notch 42 b to the positive pressure surface 42 p and the negative pressure surface 42 q, respectively, are rounded to have a smooth and curved surface. This allows the air flow X that flows into the notches 42 b from outside of the blade 42 to flow smoothly into the impeller 41 along the negative pressure surface 42 q and the positive pressure surface 42 p. This reduces the collision loss generated when air flow X flows from outside of the blade 42 to the notches 42 b. As a result, the required increase in power output from the electric motor driving the crossflow fan 4 caused by the formation of the notches in the blades 42 can be reduced. Particularly, since the negative pressure corner 42 m and the positive pressure corner 42 n are both rounded in the present embodiment, the collision loss generated when the air flow X flows from outside of the blade 42 is reduced, and required increased power output from the electric motor driving the crossflow fan can be reduced.

(2) The notches 42 b are V-shaped when viewed from the negative pressure surface 42 q and the positive pressure surface 42 p of the blade 42. Thus, a sufficient pressure receiving area for the blade 42 is ensured.

The air conditioner of the present embodiment has the crossflow fan 4, which achieves the advantages (1) and (2). The air conditioner therefore achieves the same advantages as the advantages (1) and (2).

The present invention is not limited to the above embodiment, but can be modified in various forms within the spirit of the present invention. The modifications are not excluded from the scope of the present invention. For example, the above embodiments may be modified as follows.

In the above embodiment, the negative pressure corner 42 m and the positive pressure corner 42 n are both rounded. Instead, only one of the negative pressure corner 42 m and the positive pressure corner 42 n may be rounded. FIG. 8 illustrates a configuration in which only the negative pressure corner 42 m is rounded. FIG. 9 illustrates a configuration in which only the positive pressure corner 42 n is rounded. Even with these configurations, the increase in power output required from the electric motor driving the crossflow fan 4 caused by the formation of the notches in the blades 42 can be reduced.

As shown in FIG. 10, the bottom 42 y of the notch 42 b may be formed as a smooth curved surface that protrudes outward as a whole. This structure allows the air flow X that flows into the notches 42 b from outside of the blade 42 to flow smoothly along the negative pressure surface 42 q or the positive pressure surface 42 p and into the impeller 41. This further reduces the collision loss generated when air flows into the notches 42 b from outside of the blade 42. As a result, required increased power output from the electric motor driving the crossflow fan can be reduced.

In the above illustrated embodiments, the notches 42 b are V-shaped when viewed from the negative pressure surface 42 q and the positive pressure surface 42 p of the blade 42. However, this configuration may be changed. For example, as shown in FIGS. 11 to 13, notches 42 b may have a rectangular shape as viewed from the negative pressure surface 42 q and the positive pressure surface 42 p of the blade 42. A cross sectional view taken along line 5-5 of FIG. 12 is the same as FIG. 5. Even if the notches 42 b are rectangular, the increase of the power output of the electric motor driving the crossflow fan 4 caused by the formation of the notches in the blades 42 can be reduced, as long as at least one of the negative pressure corner 42 m and the positive pressure corner 42 n is rounded. Further, when the notches 42 b are formed to be rectangular, the bottom 42 y of the notch 42 b may be formed as a smooth curved surface that protrudes as a whole outward of the impeller 41. 

1. A crossflow fan comprising an impeller having a plurality of support plates located on a rotation axis of the impeller and a plurality of plate-like blades provided at peripheral portions of the support plates, the blades extending parallel to the rotation axis, each blade being inclined such that its outer edge is located on the leading side of its inner edge with respect to the rotation direction of the impeller, one of the faces of each blade that is on the leading side of the rotation direction of the impeller forms a positive pressure surface, the face on the trailing side of the rotation direction forms a negative pressure surface, the crossflow fan being characterized in that a plurality of notches are formed at the outer edge of each blade, the notches being arranged at predetermined intervals along the rotation axis of the impeller, wherein at least one of a positive pressure corner and a negative pressure corner, which connect the bottom of each notch with the positive pressure surface and the negative pressure surface, respectively, is rounded.
 2. The crossflow fan according to claim 1, characterized in that the negative pressure corner, which connects the bottom of each notch with the negative pressure surface, is rounded.
 3. The crossflow fan according to claim 1 or 2, characterized in that the positive pressure corner, which connects the bottom of each notch with the positive pressure surface, is rounded.
 4. A crossflow fan comprising an impeller having a plurality of support plates located on a rotation axis of the impeller and a plurality of plate-like blades provided at peripheral portions of the support plates, the blades extending parallel to the rotation axis, each blade being inclined such that its outer edge is located on the leading side of its inner edge with respect to the rotation direction of the impeller, one of the faces of each blade that is on the leading side of the rotation direction of the impeller forms a positive pressure surface, the face on the trailing side of the rotation direction forms a negative pressure surface, the crossflow fan being characterized in that a plurality of notches are formed at the outer edge of each blade, the notches being arranged at predetermined intervals along the rotation axis of the impeller, wherein the bottom of each notch is formed as a smooth curved surface that protrudes as a whole outward of the impeller.
 5. The crossflow fan according to claim 1, characterized in that each notch is V-shaped as viewed from the negative pressure surface and the pressure surface of the blade.
 6. An air conditioner characterized by the crossflow fan according to claim
 1. 